My Demon Lord and I Are Each Other's Substitute [Western Fantasy]

I write both BL and straight romance, so don't read this if that bothers you.

My next BL novel: Mr. Lin's Cute Weaknesses, a cozy everyday romance about a younger man with a secret crush.

Blurb:

After dying of illness, Gu You transmigrates into a fantasy adventure novel. He plans to find the protagonist, a future winner in life, and attach himself to his coattails.

On the first night of his journey, Blaze, who will one day become the Demon King in the novel, suddenly appears and throws his arms around Gu You. His voice trembles as he says, "You're finally back!"

Apparently, Blaze has mistaken him for the Demon King's beloved, the one who got away. This person looks exactly like him and even has the same name.

Uh, did a fantasy adventure just turn into a substitute romance?

Thank you for asking. I'm Gu You, and this is my first time transmigrating. I'm not your beloved!

Injured Blaze: Weak, pitiful, helpless.

Gu You's heart softens. Demon King or hero, who says it has to be one or the other? He's determined to stuff the hero's role into the Demon King's hands!

But Blaze seems to see him only as a substitute...

That is, until Gu You gets tired of being a substitute, has a complete falling-out with Blaze, and successfully latches onto the protagonist's coattails.

After adventuring all the way to the castle of the legendary vampire count, they find...

No vampire count. In the center of the castle, Blaze spreads his black wings before Gu You, revealing horns, fangs, and blood-red eyes.

Gu You: ...

His teammates: Launch an attack, but make Gu You the target!

When Gu You opens his eyes again, he finds himself ten years in the past, facing a young Blaze.

Oh my god, it really seems like I'm the one he loved all along!

*

Blaze once fell in love with someone named Gu You, the person who saved him.

When Gu You was asked why he had saved him, he said, "Because you remind me of my friend."

That "friend" weighed on Blaze's mind for ten years. Ten years later, he saw Gu You again, but Gu You had completely forgotten him.

*One-on-one romance from beginning to end; both are each other's first love.

Theme: Only seeds nurtured by love can bloom.